This invention relates to spacecraft power systems, and, more particularly, to a method of powering a spacecraft with extended-life operation of the spacecraft batteries.
Spacecraft such as geosynchronous communications satellites require large amounts of power for the amplifiers and other electronics that relay signals from point to point on the earth's surface. The power is normally generated by solar cells mounted externally on the satellite and facing toward the sun. The solar cells produce power only when sunlight is incident upon the solar cells, and do not generate power when the satellite is in the earth's shadow.
The satellite's communications relay capabilities must continue to function when it is in shadow. A battery is provided onboard the spacecraft to receive and store excess power generated by the solar cells when the spacecraft is in sunlight, and to deliver that power to the power-consuming components when the spacecraft is in shadow. The battery therefore performs a charging/discharging cycle during periods when the satellite passes between sunlight and shadow. The battery also provides additional power for the operation of stationkeeping engines and backup power in other events.
Communications satellites are placed into geosynchronous orbit for expected periods of about 15 years or more. Because they are not readily accessible for repairs, the spacecraft systems, including the battery, must be operable and reliable for such extended periods of time without repair. Designed-in functional redundancy aids in achieving these goals, but it is highly desirable that the spacecraft systems, including the battery, have an expected operational life of at least 15 years or more.
The spacecraft batteries in use on today's orbiting communications satellites have well-established reliability records. However, there is a strong interest in using improved batteries incorporating advanced technologies to achieve higher energy storage capabilities per unit weight of the batteries, in order to reduce the relative weight of the batteries and provide greater communications relay capability. These improved batteries do not have the established reliability records of the existing batteries, simply because they are newer technologies. For this reason, there may be reluctance to use such improved batteries, even though they offer significant potential benefits in the spacecraft systems.
There is a need for an approach for battery utilization to achieve long-term operating lives, so that the batteries may be used in spacecraft applications. The present invention fulfills this need, and further provides related advantages.